A common practice in forming fibers of mineral material, such as glass fibers, is to discharge the molten glass into a rotating centrifuge or spinner. The spinner has an orificed peripheral wall, and the molten glass passes through the orifices to produce glass fibers. The spinner is mounted for rotation on a quill, and the quill is attahced via a threaded insert to a rotatable drive member, such as a locking cap. The locking cap is usually rotated with a conventional pulley, belt and motor. Since the life of a spinner is limited, the threaded insert which transmits the driving force from the locking cap to the quill, is threaded for insertion into the locking cap. Thus, when a spinner wears out, its quill and threaded insert can be simply unscrewed from the locking cap.
One of the problems associated with operating glass fiber forming equipment is that the threadable engagement of the quill and the threaded insert with the locking cap does not enable a secure locking mechanism during high-speed rotation of the apparatus. When rotated in one direction, the threaded insert is merely forced into tighter threadable engagement with the driving locking cap. But when the apparatus is to be rotated in a reverse direction the tendency is for the threaded insert to be unscrewed, thereby disengaging the threaded insert and quill from the locking cap. Thus, there is a need for means for enabling the threadable engagement of the threaded insert with the locking cap, and at the same time provision for locking the threaded insert and the locking cap to prevent relative movement to each other during high-speed rotation.